Centrifugal pump and method of manufacture therefor



July 10, 1956 K. R. LUNG CENTRIFUGAL PUMP AND METHOD OF MANUFACTURE THEREFOR 6 Sheets-Sheet 1 Filed Jan. 21, 1952 FIG-I FIG INVENTOR KENNETH RAYMOND LUNG BY 72 644 1 7' I;

ATTORNEYS K. R. LUNG July 10, 1956 CENTRIFUGAL PUMP AND METHOD OF MANUFACTURE THEREFOR Filed Jan. 21, 1952 6 Sheets-Sheet 2 O 6 8 m 8 M 8 R 0 m A K i m l N 1 f [1 :III E W /V. J. u x M 4 o 8 6 O o 3 4 i Q e 9 8 9 z 4.. 2 4 O \k 1 O s 7 IIIIIIl-llll 2 6 3 4 KENNETH RAYMOND LUNG M' 7* ATTORNEYS July 10, 1956 K. R. LUNG 2,753,307

CENTRIFUGAL PUMP AND METHOD OF MANUFACTURE THEREFOR Filed Jan. 21, 1952 6 Sheets-Sheet 3 B x. l A

64 66F A I Q; N F IG-3 Q w QI t 4 NW:

INVENTOR I KENNETH RAYMOND LUNG 40 BY fww'fl -6 a.

' ATTORNEYS M 10, 1956 K. R. LUNG 2,753,807

CENTRIFUGAL PUMP AND METHOD OF MANUFACTURE THEREFOR Filed Jan. 21, 1952 6 Sheets-Sheet 4 FIG-l7 INVENTOR KENNETH RAYMOND LUNG BY W :44;

ATTORNEYS July 10, 1956 v K. R. LUNG 2,753,807

CENTRIFUGAL PUMP AND METHOD OF MANUFACTURE THEREFOR Filed Jan. 21, 1952 6 Sheets-Sheet 5 FIG-6 INVENTOR KENNETH RAYMOND LUNG BY W W ATTORNEYS y 10, 1956 K. R. LUNG 2,753,807

CENTRIFUGAL PUMP AND um'aon OF MANUFACTURE THEREFOR Filed Jan. 21, 1952 s Sheets-Sheet e FIG-l3 INVENTOR ji KENNETH RAYMONDLUNG BY a. 774-3L ATTORNEYS United States Patent CENTRIFUGAL PUMP AND METHOD OF MANUFACTURE THEREFOR Kenneth R. Lung, Dayton, Ohio, assignor to The Tait Manufacturing Company, a corporation of Ohio Application January 21, 1952, Serial No. 267,443

9 Claims. (Cl. 103108) This invention relates to centrifugal pumps and particularly to centrifugal pumps of the type composing individual pumping units which can be stacked together to make a multi-stage pump.

Centrifugal pumps are well known in the art and are manufactured in great quantities for the purpose of pumping fluids, such as in connection with water systems wherein water is to be pumped from a well or the like.

Heretofore, it has been customary to manufacture such a pump by casting the impeller and the associated parts of the pump, such as the casing within which the impeller runs. Pumps manufactured in this manner are quite satisfactory for the general purpose of pumping fluids, but castings are relatively expensive, there is a great deal of scrap, it is difiicult to hold extremely close limits during manufacture, and the surface of such a member is fairly rough unless the part is made by expensive die casting systems.

The primary object of the present invention is to provide a pump of the nature described, constructed according to improved manufacturing techniques employing pressed metal parts for forming important elements of the pumping units.

Another object is the provision of an improved centrifugal pump and a method of manufacturing the same which will overcome the drawbacks referred to above.

A particular object of the present invention is the provision of a greatly improved arrangement for leading the fluid pumped from the impeller of a pumping unit into the inlet of the next pumping unit, or into a discharge chamber.

Still another object of this invention is the provision of a centrifugal pump which is exceedingly eflicient in operation and which feature is of particular importance in connection with small pumps in which small loss of power represents a substantial percentage of the power input.

Still another object of this invention is the provision of an improved arrangement for a centrifugal pump adapted for being used with a jet pump as regards the connection of the conduits extending between the pumps.

Another particular object oif this invention is the provision of an improved arrangement for priming the centrifugal pump.

Still another object of this invention is the provision of a method of pumping fluid in which the energy of the pumped fluid is employed for assisting in directing the fluid to the next stage of the pump.

A still further object of this invention is the provision of an improved bearing for the shaft of a centrifugal pump of the nature described which is self-lubricating during operation of the pump.

These and other objects and advantages will become more apparent upon reference to the following description taken in connection with the accompanying drawings, in which: I

Figure 1 is a perspective view showing a centrifugal 2,753,807 Patented July 10, 1956 "ice pump according to this invention, with a drive motor mounted thereon;

Figure 2 is a sectional view indicated by cutting plane 22-2 on Figure 1, showing the pumping mechanism in transverse section;

Figure 3 is a sectional view similar to Figure 2, but showing the arrangement at the bottom of the base casting of the pump for connecting thereto the drop pipe leading into the well and the connection of the pipe leading to the jet pump in the well;

Figure 4 is a view looking up at the bottom of the base casting and the pump and is indicated by line 4-4 on Figure 3;

Figure 5 is a sectional view indicated by line 55 on Figure 2 and shows the compartment cored in the base casting by means of which priming fluid can be directed to the inlet of the pump;

Figure 6 is an exploded perspective view showing the several parts that go to make up one pumping unit of the pump in disassembled relation;

Figure 7 is a plan view looking down on top of a diffusor plate forming the discharge element from each of the pumping units as it is constructed according to my invention;

Figure 8 is an exploded perspective view showing the two component parts of the diflusor plate of Figure 7 in disassembled relation;

Figure 9 is a fragmentary perspective view drawn on an enlarged scale and showing the said component parts of the diffusor plate during the act of assembling them together;

Figures 10, ll, 12 and 13 are sectional views taken through a flow passage of the diffuser plate and are indicated by lines 10-10, 11-11, 1212 and 1313 respectively, on Figure 7;

Figure 14 is a sectional view indicated by line 1414 of Figure 7, showing one of the passages through the diffusor plate in section from end to end;

Figure 15 is a plan view of an impeller adapted for use in the pump and which impeller is constructed principally of sheet metal parts;

Figure 16 is a sectional view through the impeller of Figure 15 and is indicated by line 1616 thereon;

Figures 17, 18, 19 and 20 are views showing the lower member of the ditfusor plate in the various stages of its manufacture;

Figure 21 is a fragmentary sectional view showing a modified construction of the pump according to this invention;

Figure 22 is a fragmentary view showing a manner of sealing the pump according to my invention; and

Figure 23 is a perspective view similar to Figure 18, but showing the lower member of the diffusor plate being formed with slots therein instead of incisions.

Referring to the drawings somewhat more in detail, and particularly to Figures 1 through 5, a pumping unit constructed according to the present invention comprises a base or suction casting 10, an upper or discharge casting 12, a cylindrical sleeve 14 extending between the said castings and bolts 16 that hold the castings and sleeve in assembled relation. Gasket means at 18 are provided for sealing where the sleeve abuts the castings and between bolt 16 and casting 10 to prevent any leakage of fluid from within the sleeve.

The discharge casting 12 is adapted for supporting the drive motor 20 which is attached thereto, as by bolts 22, and the drive shaft 24 of the motor extends downwardly into a space defined by the discharge casting. Shaft 24 is secured to drive shaft 26 of the pump by a coupling member 28 which is located in position by set screws 30.

According to the present invention there is arranged within sleeve 14 one or more pumping units generally indicated by reference numeral 32 and which will be described more in detail hereinafter. The lowermost of the pumping units 32 has its inlet in fluid communication with the inlet passageway 3 of base casting 16 which terminates at the extreme lower surface of the base casting in an inlet port so. The uppermost of the said pumping units 32 discharges its fluid into the discharge chamber 38 in discharge casting 12 and which comprises a threaded outlet port 4t adapted for receiving a discharge conduit.

The discharge casting 12 comprises an annular ledge or flange 42 that engages the upper portion of the uppermost of the pumping units 32 whereby the said pumping units are clamped in position in the pump between the said flange and the upstanding annular portion 44 forming an extension of inlet passageway 34.

About the periphery of discharge casting 12 the chamber 38 thereof communicates with the interior of sleeve 14 as by one or more openings, as indicated at 46. The provision of openings 45 insures that during operation of the pump, sleeve 14 will become completely filled with the pumped fluid, for example, water, and which fluid can subsequently be used for priming the. pump should it become necessary.

The construction which permits this priming is illustrated in Figure and comprises an elongated chamber 48 formed in the base casting and in direct communication with inlet passage 34. At one side of the base casting chamber 48 has a Wall 5% with an aperture at 52 that communicates with the space inside sleeve 14. Cone pointed screw 54 is threaded through the outer wall of the base casting and serves as a ready means for opening aperture 52 to permit priming of the pump, or for closing the said aperture when priming is not desired or necessary.

It has been mentioned that the pump of this invention is adapted for use in connection with a jet pump as may be required for increasing the rate of fluid flow or for obtaining the proper amount of lift to effect pumping, and according to the present invention, an improved construction is provided for connecting the drop pipe leading into the well and the pipe leading to the jet of the jet pump. conventionally, these connections are effected by means of an auxiliary slip joint unit that is not directly connected with the pump structure. According to the present invention, however, such additional members are not required and, instead, the slip joint is provided integrally with the base casting. This is best illustrated in Figures 3 and 4.

In these figures it will be noted that the bottom surface of the discharge casting, and through which surface the inlet port 36 opens, is adapted for receiving a flat flange 56 to be retained in position on the bottom of the discharge casting by the cap screws 5%. Flange 56 is threaded at 69 for receiving the drop pipe 62 and adjacent the said drop pipe is bored and threaded for receiving the resilient packing 64 and the gland 66 for compressing the packing about the pipe nipple 68. This construction provides a slip joint for receiving nipple 68 so that connection can be made thereto after the drop pipe 62 is in place.

Nipple 68 is preferably arranged for connection with conduit 7t? that leads to the jet of the jet pump by means of a coupling or union 72. The described arrangement is such that connection of the pump to the pipes leading into the well can be quickly and easily effected and without the use of additional fittings, such as the slip joint referred to.

The location of the pump vertically with. regard to the well over which it is positioned can advantageously be effected by short lengths of pipe 74 providing legs for the pump and threaded into the tapped bores, 76. This forms a simple and effective means of supporting the pump and its position vertically can be adjusted merely by changing the lengths of the pipe legs 74.

Turning now to the pumping unit that forms the heartof a pump, according to the present invention, these units comprise, as will best be seen in Figures 2 and 6; an outer case element 80, an impeller 82 rotatable within the case element, a diffusor plate structure 84 above the impeller and within the case, and a cover element 86.

According to the present invention, at least the case, diffuser plate, and cover are formed by pressing them from sheet metal, steel where permissible, and a corrosion resisting alloy or brass where conditions dictate the use of such a material. Many advantages obtain from pressing the pump parts from sheet metal. The parts themselves are less expensive than when they are cast and a great deal of machining that must be done on cast members is eliminated, inasmuch as the pressed metal parts are ready for use with substantially no further work to be done thereon when they are taken from the forming die.

An extremely important feature in connection With the pressed metal parts is that their surface is inherently smooth as compared with the rough surface associated with a casting and because of this, there is a great deal less friction to fluid flow within the pump and a higher efficiency obtains. This is particularly true in connection with the smaller pumps, because the inherent roughness referred to is relatively larger in the small flow passages of the smaller pumps than it is in the large flow passages of the larger pumps, and thus, a higher percentage of the power input is dissipated in overcoming the said friction.

Tests indicate that a good degree of efiiciency for a small pump, such as is employed in domestic water systems, is about 45% when the pump is constructed in the conventional manner with castings. However, with a pump constructed according to the present invention with pressed sheet metal parts, even a relatively crude test model was found to exhibit an efliciency in excess of 65%. It will be understood, of course, that as the sizes of the pumps increase, this differential in efliciency would decrease.

Still another advantage that obtains from the forming of the pump parts by pressing from sheet metal is that the parts will come from the forming dies substantially the same size and shape until the said dies are badly worn, and this enables the parts of the pump to be located directly on one another without there being any machining operations carried out on the parts after they are removed from the forming die.

The sheet metal parts are also substantially thinner and lighter than it is possible to make corresponding parts by casting, and inasmuch as sheet stock of the type that would be employed, is extremely uniform, the amount of scrap that occurs during manufacture is much less than is encountered with castings.

Turning again to the pumping units, the casing 89- thereof is a relatively deep pan-shaped or dish-shaped element having a central inlet aperture comprising an axially extending flange 88. The outer rim part of the case also comprises an axially extending flange 9'0 that is offset radially outwardly from the side wall of the case. It will be evident that the case is of such a configuration that it can readily be blanked and drawn from sheet stock according to conventional metal working practices.

The axial flange 88 at the inlet side of the case telescopes into the inlet opening at'the upper end of passage 34, as will be seen in Figure 2.

The flange 90 at the upper edge of the case provides a peripheral surface that receives and locates cover 86 for the pumping unit. Cover 86 also comprises an axially extending peripheral flange 92 fitting closely Within. the flange 90. The said cover also comprises an. outer slightly downwardly inclined portion 94 that forms a surface for supporting the case 80. of the next pumping unit thereabove.

Cover 86 also includes an inner annular part. 96 that is displaced downwardly from the annular. part 94 and which terminates at the center in an upturned annular arr-sass? g flange 98 adapted for closely receiving the axially extending flange 88 of the case of the next pumping unit. This engagement of flanges 88 and 98 provides means for radially locating the case of the second pumping unit on the cover of the first pumping unit and which cover it, in turn, radially located on the case of its unit by the interengaging flanges 90 and 92. Cover 86 also locates the case 88 of the next pumping unit thereabove in the axial direction by engagement with the lower surface thereof.

The uppermost of the pumping units, and it will be understood that can be as many of the units as desired within the pump merely by selecting the proper length for sleeve 14 and shaft 26, does not include a cover, but instead, there is an annular resilient rubber-like ring 100 that engages beneath annular flange 42 and on top of the ledge formed in the case at the bottom of flange 90, and thereby retains all of the pumping units in assembled relation in the pump. It it to be noted that no bolts, screws, fasteners of any sort, or brazing or welding is required and that no portion of any of the cases of the pumping units are threaded or otherwise modified in order to provide for an assembled pump.

Within each pumping unit is an impeller 82 and these impellers are mounted on the shaft 26 which has its lower end journaled in a bearing 102 carried in a pocket provided therefor in the base casting 10. Bearing 102, according to my invention, is adapted for being lubricated by water, and to this end the bearing pocket is apertured at its bottom end at 104 and a felt plug 106 is placed beneath the lower end of the shaft and bearing in the pocket.

Felt plug 106 acts as a filter plug and permits only pure water, free of foreign material, to gain access to the bearing. The suction developed by the pump in operation will cause water to be drawn from the inlet passage through aperture 104 and filter plug 106 up through bearing 102 and thereby lubricate the said bearmg.

Each pumping unit also comprises a diflusor plate which is of a novel construction according to the present invention. The ditfusor plates are identified by the reference numeral 84 in Figure 2 and detailed showing of the diffuser plate and its construction will be found in Figures 7 through 14.

The ditfusor plate comprises a lower plate portion 110, generally pan-shaped, with a central aperture 112 for admitting the hub of the associated pump impeller and defined by the axial flange 114. Each of the plates 110 has formed about its periphery a plurality of tapering angular recesses 116. As will be seen in Figures 8 through 14, these recesses are formed upwardly into the outer corner of the plate 110 and at their ends open to the upper surface of the plate through the apertures 118.

The other part of the diffusor plate structure comprises an upper plate 120 having a central aperture 122, as shown in Figure 8, defined by the axial flange 124 which is of a size closely to receive flange 114. About the periphery of plate 120 there are a plurality of upstanding arcuate portions 126 which vary in axial length from one end to the other and from the upper edges of which there project radially outwardly the flat portions 128. The purpose of upper plate 120 is to provide for a continuation of the passages formed by the recesses 116, whereby the discharge from the impeller beneath the diifusor plate is directed to the upper surface of the diflusor plate. Due to the fact that the passages expand, both radially and axially, they serve to slow the fluid down and to convert its kinetic energy into a pressure head and also serve to direct the fluid inwardly toward the inlet of the impeller of the next stage.

As will be seen in Figures 7, 8 and 9, the radial tapering of the ditfusor passageways comes about by the formation of the upstanding portions 126 so that they spiral inwardly toward the center of the difiusor plate in the direction of fluid flow in the manner illustrated. Due to the expanding of the diffusor passageways, substantially all of the kinetic energy of the pumped fluid is converted to pressure energy at the time the fluid is discharged from the ends of the passageways.

The upper plate of the diffusor plate structure advantageously comprises a plurality of upturned tabs which assist in directing the pumped fluid inwardly to the inlet of the next impeller. These vanes may be straight or curved, but are preferably straight, as illustrated, for ease of formation.

In the assembling of the lower and upper plates of the diffuser plate structure, the upper plate is placed on the lower plate with the ends of the recesses 116 abutting the rear ends of the portions 126 and 128 of the upper plate. The appearance of the plates, as these parts are brought into engagement, is illustrated in Figure 9-. After the plates have been brought into proper engagement, they are preferably interconnected by welding, brazing or soldering, whichever is preferred, along the points of abutment indicated by the brackets 132, in Figure 7. This results in an integral structure and prevents the plates from becoming misaligned.

It will be understood that it is not absolutely essential to provide for the connection referred to between the upper and lower parts of the diffuser plate, since the manner in which they are manufactured will insure that the lines of abutment between the two members will form relatively good fluid seals and smooth passages for the flow of fluid. It will accordingly be understood that the integral interconnection between the two plates can be replaced by any other arrangement for retaining the plates in proper register.

There is illustrated in the drawings a diflusor plate having four passageways extending therethrough, but there could be provided a greater or lesser number, if desired. Tests have indicated that four passageways is a practical number with a good efliciency obtaining and with the costs of manufacture being kept within reasonable limits.

As will be seen in Figure 2, the diflusor plate structure has an outer peripheral portion fitting closely within the inner periphery of the straight side wall part of the case element 80. This locates the diftusor plate structure radially, and for locating the said structure axially, the upper peripheral edge of the dilfusor plate structure is formed outwardly so as to fit over the ledge extending about the cover element between the above-mentioned side wall portion and the axial flange portion 90.

In order to provide for a proper clearance between the hubs of the impellers and the apertures in the case elements of the pump units and the diflusor plate structures thereof, there may be provided the bushings 134, as illustrated in Figure 2, and which are pressed into the case members and the diflusor plate structures with a fairly close running clearance about the impellers.

The arrangement of the bushings 134 in Figure 2 may be replaced by the bushing arrangement illustrated in Figure 21, wherein bushing 136 which provides for the close running fit about the hub of the impeller, also provides the means for radially locating the case 138 of the upper pumping unit on the cover 140 of the lower pumping unit. In all other respects the pumping unit of this arrangement is identical with those of Figure 2.

The pumping units of the present invention are well adapted for the construction of a sealed unit due to the manner in which the cover, case, and the ditfusor plate structure interfit. This is illustrated in Figure 22, wherein the resilient annular sealing ring 142 is interposed into the space between the cover 144 and case 146 about the periphery of the outturned lip about the upper edge of the diflusor plate structure 148.

It will be understood that normally such sealing would not be required because of the fluid standing within the sleeve 14 and surrounding all of the pumping units. In certain cases, however, it might be advisable to provide such a sealing element, and the arrangement of this invention is ideally suited to that purpose.

The impellers illustrated in Figure 2 are of the cast type, but according to this invention, the impellers, as well as the other portions of the pumping units, could be substantially entirely constructed of pressed sheet metal. Such an impeller is illustrated in Figures 15 and 16, where it will be seen to comprise a back plate 155 a front plate 152, and a plurality of curved plates or vanes 154, which are preferably staked to the front and back plates, as at 156, all the said parts being formed of sheet metal. Back plate 15% preferably has pressed therein and welded thereto, a hub 158 of sufficient thickness to provide for the required strength that must be present in the impelle at that point.

According to the present invention, the preferred method of manufacturing the lower plate of the diffuser plate structure is illustrated in Figures 17 through 20. in Figure 17, the part shown is a blank 160. In Figure 18, blank 161i is cut with a plurality of incisions, as at 162. The purpose of these incisions is to provide for the apertures at the end of the passages in the plate, and are cut completely to the periphery of the plate so that on subsequent fo'rming operations, there will be no tearing or warping of the metal of the plate.

In Figure 19 the plates have been formed with the bentin passages 164 and with the out-turned upper lip 166. It will be noted that due to the difference in configuration of the plate on opposite sides of the cuts 162 therein, there is a radial offset 168, at each of the said cuts. Each plate formed to the stage illustrated in Figure 19 is of larger diameter than is required, and the last operation performed is one of trimming which produces the final workpiece, as illustrated in Figure 20. The cuts 162 will be found to fit quite closely together and therefore need not be sealed after the plate has been formed.

Still another manner of forming the diffuser plate is illustrated in Figure 23, and in which it will be seen that instead of the incisions 162 formed about the periphery of the plate, there are provided the slots 184 which do not extend completely to the periphery. These slots permit the forming of the tapering channels about the periphery of the formed plate, but permit the rim part thereof to be continuous whereby the forming of the plate does not introduce the offsets about the periphery, as are indicated at 168 in Figure 19.

While the difiusor plate has been illustrated and described as comprising the lower part 110 and the upper part 120, it is to be understood that this invention also contemplates the diffusor plate consisting solely of the lower portion ill). The removing of the upper part 12% from the diflusor plate assembly does decrease the overall efiiciency of the pumping unit, but this decrease of efiiciency is of a comparatively minor nature, and in many instances, the economy of leaving ofif the top plate portion of the diffusor plate would be justified because of the relatively minor decrease in efliciency.

It will be understood that it is desired to contemplate within this invention the arrangement of the diffusor plate, both with the top plate portion that provides for extensions of the tapering passageways, and without the said top plate.

It will be understood that this invention is susceptible to modification in order to adapt it to difierent usages and conditions, and, accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

I claim:

1. In a centrifugal pump; a diffuser plate structure comprising a pair of interfitting members defining a plurality of circumferentially extending passageways starting on the underneath surface of the structure and terminating on the upper surface of the said structure, said passageways expanding bothaxially and radially inwardly toward their discharge ends, and the discharge end of each passageway overlapping the inlet end of the next passageway.

2. In a centrifugal pump; a diffusor plate structure comprising a first plate having a flat bottom and an axially extending peripheral. portion, a plurality of indentations extending circumferentially about the periphery of the plate and tapering upwardly to an end point of maximum depth where an opening in a plane normal to the said bottom is established, a second plate mounted on top of said first plate and having peripheral portions communicating with the ends of the said indentations, the said peripheral portions of the second plate providing for continuations of the passages formed by the indentations and expanding both axially and radially inwardly.

3. A diffuser plate structure for a centrifugal pump; a first plate having a flat bottom and an axially extending peripheral portion, a plurality of uniformly circumferentially spaced tapering indentations formed in the said flat bottom portion about the periphery thereof, each said indentation terminating at itsv point of maximum depth in an opening opening to the-upper side of the plate, a second plate mounted on top of the first plate and having peripheral portions abutting at their one ends, the ends of said indentations and said portions expanding both axially and radially inwardly whereby to form with the lower plate a plurality of dilfusor passageways for conducting fluid pumped beneath the plate into the space above the plate and for converting kinetic energy thereof to a pressure head.

4. A pressed metal diffusor plate structure for a centrifugal pump; a lower plate having a flat bottom, a peripheral flange extending axially upwardly from said flat bottom, and a radial flange projecting outwardly from the upper edge of said axial flange, said plate having a plurality of uniformly spaced tapering indentations formed upwardly in the periphery of said flat bottom, each said indentation terminating in an opening at its point of maximum depth disposed in a plane perpendicular to said bottom, the maximum depth of said indentations being less than the length of the said axial flange, a second plate mounted on top of said first plate and having a plurality of peripheral portions thereon adapted for abutting the ends of the indented portions on the lower plate to form continuations of the passages formed thereby, the peripheral portions of said upper plate forming passages that expand both axially and radially, means integrally uniting said plates, and guide vanes upstanding from the upper plate for deflecting the fluid inwardly toward the inlet opening of the next pumping stage.

5. In a diffuser plate structure for a centrifugal pump; a first pressed metal plate having a plurality of incisions circumferentially spaced thereabout and extending radially inwardly, said plate being formed with a flat bottom and an axially extending peripheral portion, a plurality of indentations formed in the plates about the periphery of the flat bottom thereof, each said indentation tapering from a point between an adjacent pair of said incisions in one direction to a point of maximum depth at the next said incision whereby a tapering passageway connecting the bottom of the plate with the top thereof are formed, a second plate mounted on top of the first plate and having a plurality of upstanding peripheral portions engaging the ends of the said indentations in the first plate, said peripheral portions spiraling inwardly of the upper plate, and each of said peripheral portions having an upper part extending radially outwardly into engagement with the periphery of the axially extending portion of said first plate, the said portions of the second plate providing continuations of the said passageways that expand both axially and radially inwardly, and generally radially extending guide vanes upstanding from the said second plate.

6. In a centrifugal pump having a plurality of pumping stages in axial alignment; a plurality of housings, one

for each stage, and each said housing comprising a plurality of pressed sheet metal parts having interfitting abutting engagement with each other, each housing having a centrally located inlet on one side, said housings being in stacked relation, a discharge member abutting the outer periphery of the stacked pumping units at one end, a suction member abutting the stacked pumping units at the other end, said suction member engaging the adjacent unit in the center about the inlet thereof, and means interconnecting said suction and discharge members for clamping the said pumping units therebetween, there being an imperforate sleeve surrounding said pumping units in spaced relation therewith and having sealing engagement at its opposite ends with said suction and discharge members, said suction member having a flow passage therethrough to the inlet of the first pumping stage, said discharge member having a flow passage therethroug-h to the discharge side of the last pumping stage, and means for communicating the flow passage in the discharge member with the interior of said sleeve.

7. In a centrifugal pump having a plurality of stacked pumping units; a housing for each said unit of interfitting abutting pressed metal members, the members comprising a case having a central inlet opening with an axially projecting flange, and a cover thereon having an outlet opening with an axial flange, the flange on the cover being of a size for closely telescoping the flange on the case, a suction member having a flow passage therethrough adapted for receiving at its upper end the flange about the inlet opening of the case of the first pumping unit, a discharge member adapted for receiving the upper peripheral portion of the case of the last pumping unit, a resilient annular sealing ring between the discharge member and the said peripheral portion of the case of the last pumping unit, an imperforate sleeve surrounding the said units in radially spaced relation and extending between the suction and discharge members, means connecting said suction and discharge members together to form a unitary structure, a discharge passage in the discharge member communicating with the outlet of the last pumping unit, and means connecting the discharge passage with the interior of said sleeve.

8. In a multistage centrifugal pump having a main housing and including a plurality of centrifugal impellers arranged in axially spaced relation along a drive shaft and each constructed to discharge in planes extending radially of said shaft, the combination of a plurality of individual casings each associated with one of said impellers, each said casing being of cup shape including a. main substantially cylindrical portion surrounding the periphery of said associated impeller and a smaller end portion defining the inlet to said impeller, difluser means associated with each said casing and including portions interfitting with each said casing and the adjacent said casing in the downstream direction, each said difiuser means including portions defining passages for conducting the discharge from each said casing to said inlet of said adjacent casing, and means maintaining said casings and said diffuser means in stacked relation within said pump housing.

9. In a multistage centrifugal pump having a main housing and including a plurality of centrifugal impellers arranged in axially spaced relation along a drive shaft and each constructed to discharge in planes extending radially of said shaft, the combination of a plurality of individual casings each associated With one of said impellers, each said casing including a substantially cylindrical middle portion surrounding the periphery of said associated impeller, each said casing including an inlet end portion of smaller diameter than said middle portion defining the inlet to said associated impeller, each said casing including an outlet end portion of larger diameter than said middle portion and connected with said middle portion by an annular seat, diffuser means associated with each said casing and including a portion adapted to engage said seat of said associated casing to close said casing, each said diifuser means including a portion adapted to interfit with said inlet end portion of the adjacent said casing in the downstream direction, each said diffuser means including portions defining passages for conducting the discharge from said associated casing to said interfitting inlet of said adjacent casing, and means maintaining all of said casings and said diffuser means in stacked and interfitting relation within said housing.

References Cited in the file of this patent UNITED STATES PATENTS 896,585 Salzer Aug. 18, 1908 966,428 Comstock Aug. 9, 1910 1,382,665 Myers June 28, 1921 1,914,919 Heermanns June 20, 1933 1,944,504 Greer Jan. 23, 1934 2,047,329 Peterson July 14, 1936 2,056,553 Abramson Oct. 6, 1936 2,161,695 Bigelow June 6, 1939 2,259,361 Vorkauf Oct. 14, 1941 2,282,765 Mann May 12, 1942 2,300,688 Nagle Nov. 3, 1942 2,475,118 Wolfe July 5, 1949 2,478,306 Orr Aug. 9, 1949 2,493,240 Emmert Jan. 3, 1950 2,524,770 Conery Oct. 10, 1950 FOREIGN PATENTS 297,661 Great Britain Sept. 27, 1928 342,065 Great Britain Jan. 29, 1931 

